1. Field of the Invention
The present invention relates to a headlamp for a vehicle for changing a luminous intensity distribution by moving a movable shade.
2. Description of the Related Art
According to a headlamp for a vehicle, light from a light source is reflected towards the front by a reflector to illuminate a low beam or a high beam. Because a pattern for luminous intensity distribution differs between the low beam and the high beam, it is conventional to use a light source bulb having two light sources or two light source bulbs by which the beam is switched between low intensity and high intensity.
However, there is also known a headlamp for a vehicle constituted to switch a beam by a single light source. Particularly, in a two lights type headlamp using a discharge bulb as a light source bulb, there is frequently a case in which such a constitution is obliged to construct.
For a single light source, there is known a method of switching beams by moving a movable shade as disclosed in, for example, Japanese Patent Laid-Open No. 2000-207918. According to the method, a movable shade is moved between two predetermined positions at which a differing amount of light incident on a reflector from a light source is blocked.
According to such a headlamp for a vehicle, it is preferable to make the movable shade as light as possible to reduce a switching time and to decrease the knocking sound emitted by the movable shade coming into contact with a stopper.
However, it is also important to avoid a situation where the light-weight movable shade is shifted by vibration or the like while the vehicle is running. Such a problem generally occurs when the movable shade is moved to change a luminous intensity distribution.
An object of the present invention is to provide a headlamp for a vehicle in which a light-weight movable shade can change the luminous intensity distribution without deteriorating its light blocking function.
The invention achieves the above-described object by having a predetermined strip at a movable shade.
That is, according to the invention, there is provided a headlamp for a vehicle including a light source, a reflector for reflecting light from the light source in a front direction, a movable shade for blocking a portion of the light incident on the reflector from the light source, and a shade driving apparatus for moving the movable shade between two predetermined positions. The movable shade includes a shade main body of a cylindrical shape extending substantially in a front and rear directions, and a shade leg portion extending from the shade main body to an outer side of the shade main body substantially in a direction of a diameter thereof. At least one strip extending in a peripheral direction of the shade main body is disposed at a position substantially opposite to a position of the shade leg portion in a peripheral face portion of the shade main body.
The xe2x80x9clight sourcexe2x80x9d is not limited to but can be, for example, a discharge light emitting portion of a discharge bulb or can be a filament of an incandescent bulb such a halogen bulb.
The xe2x80x9cmovable shadexe2x80x9d is not limited to a particular form as long as the shade can block the portion of light incident on the reflector from the light source bulb and the movable shade is integrally formed with the shade main body and the shade leg portion or is formed therewith separately.
The xe2x80x9ctwo predetermined positionsxe2x80x9d may be positions for forming a luminous intensity distribution pattern for low beam and for high beam by disposing the movable shade at predetermined positions. The invention may include other positions for forming other luminous intensity distribution patterns.
The xe2x80x9cshade driving apparatusxe2x80x9d is not limited to a specific apparatus as the movable shade is configured to move between the two predetermined positions. For example, the movable shade can include a solenoid or a pulse motor. Further, the movement of the movable shade in the shade driving apparatus is not particularly limited to but can include pivotal movement or linear reciprocal movement.
The xe2x80x9cstripxe2x80x9d is not particularly limited any shape as long as the strip is formed to extend at least in the peripheral direction of the shade main body. For example, a strip can be a linear shape, or a curved shape or a strip can include a main strip and a sub strip branching from the main strip.
The headlamp for a vehicle according to the invention is provided with the movable shade including the shade main body in the cylindrical shape extended substantially in the front and rear direction and the shade leg portion extended from the shade main body to the outer side substantially in the direction of the diameter. The peripheral portion of the shade main body is formed with at least one strip extending in the peripheral direction and therefore, the rigidity of the shade main body can be increased and the thin-walled formation of the shade main body can be achieved. Further, the strip is formed at a position substantially opposite to a position of the extended shade leg portion in the peripheral face portion of the shade main body, that is, at a position operated with the largest inertia load in the shade main body. Accordingly the movable shade can be restrained from shifting or vibrating while the vehicle is running. Thus, the shade""s blocking function can be effectively maintained.
Therefore, according to the invention, a light-weight movable shade can be implemented without deteriorating its light blocking function.
When the movable shade is pivotally moved in the front and rear directions with the predetermined portion of the shade leg portion as the pivotal center, a very large inertia load is carried at the position substantially opposite to the extended position of the shade leg portion in the peripheral face portion of the shade main body. Thus, the configuration of the present invention would be particularly effective in such a case.
The xe2x80x9cshade leg portionxe2x80x9d can be formed to extend in any direction relative to the shade main body as long as the shade leg portion extends from the shade main body to the outer side substantially in the direction of the diameter. However, when the shade leg portion is configured to extend to the lower side from the lower end portion of the shade main body, the strip is formed at the upper end portion of the shade main body. Thus, the rigidity of the shade main body can be increased with excellent left and right balance, thereby, shifting of the movable shade can be further restrained effectively.
When the shade main body of the movable shade is formed as a member in a cylindrical shape extending substantially in the front and rear directions as in the above-described configuration, it is preferable to provide the fixed shade on the front side for blocking direct light directed from the light source in the front direction by the fixed shade, depending on the kind of the light source. However, in order to prevent the fixed shade from interfering with the movable shade, it is necessary to provide the fixed shade at a position away from a pivotal locus of the movable shade. Consequently, the fixed shade is made large or the layout is restricted.
Hence, when a notch in a predetermined shape is formed at the front portion of the extended position of the shade leg portion in the movable shade, the movable shade interferes less with the fixed shade in pivotal movement and therefore, a small fixed shade can be implemented or the fixed shade can be provided at a position proximate to the movable shade. Further, by forming a notch, the movable shade can further be made light. In this case, the shape of the xe2x80x9cnotchxe2x80x9d can be set in accordance with the structure of the light piece to the extent that it does not deteriorate the light blocking function of the movable shade.